The present application is directed to slickwater fracturing fluids, methods of preparing them and their use for the hydraulic fracturing of hydrocarbon-producing subterranean formations.
Fracturing fluids are used in the process of hydraulic fracturing to facilitate the recovery of hydrocarbon deposits within a subterranean formation. Fracturing fluid is generally pumped into the formation at high pressure so as to force the opening of cracks or fissures within the formation, allowing hydrocarbons to flow more easily from the formation. Fracturing fluids often contain large amounts of water, although methanol or hydrocarbons such as diesel, or liquefied propane or methane can also be used. Often, fracturing fluids contain a suspended granular solid or proppant which remains in the formation once the fracturing fluid has been removed, where the proppant acts to prop open the channels which are formed. Fracturing fluids often also contain additives to control the viscosity and other properties of the fluids so that adequate quantities of proppant can remain suspended while the fluid is being pumped into the formation, but the proppant can be deposited within the cracks and fissures formed downhole and the remaining components can be readily removed from the fractured formation. Such additives can include gelling agents to increase viscosity, facilitating the suspension of proppant for transport into the formation, and breakers to reduce viscosity, thereby allowing proppant to be deposited in the fractures and facilitating the recovery of used fracturing fluid. However, some fracturing fluid additives are toxic or can cause harm to the environment.
Slickwater fracturing systems are used especially for stimulation of highly pressurized deeper shale formations, and are generally water-based fluids containing friction-reducing agents so that large volumes of fluid can be pumped rapidly through the wellbore and into the formation. Slickwater fracturing fluids often have reduced viscosity compared to other fracturing fluid systems, and therefore lower concentrations of proppant are often used so that the proppant can remain suspended to be carried downhole. Because of the large volumes of water involved, slickwater systems can pose environmental challenges, both with regard to disposal of flowback water and with regard to possible contamination of the adjacent aquifer by fluid remaining in the formation after fracturing. Recently, environmentally friendly slickwater compositions have been described in US Patent Application Publication No. 2011/0071058 and U.S. Pat. No. 7,741,252.
Therefore, there is a need for a slickwater fracturing system that addresses one or more of the disadvantages of, or provides an alternative to, present slickwater systems.